Patients with leishmaniasis were studied. Thus far the following data have been accumulated. Patients with diffuse cutaneous leishmaniasis show anergy to leishmania antigens. This anergy is antigen specific and is mediated by an adherent suppressor cell population. The defect can also be corrected by addition of prostaglandin synthetase inhibitors. A murine model for studying transfer factor (TF) was developed. TF activity is dose dependent and proportional to spleen cell equivalent. TF is antigen specific and activity can be ablated by simultaneous administration with relevant but not irrelevant antigen. TF phenomena is time dependent. A controlled clinical trial in mucocutaneous candidiasis has been conducted. The study showed that ketoconazole tablets taken orally for a 6 months period is highly efficacious in treating symptoms and signs of the disease but not curative.